Rotary engines can provide a number of advantages over reciprocating piston engines including reduced complexity and increased power for a given engine weight.
An example of a known rotary engine 100 of Wankel type is shown in FIG. 1. The engine 100 has a housing 110 and an eccentric shaft 120 that provides a drive output. The eccentric shaft 120 has a shaft portion 120′ having a longitudinal axis and an eccentric portion projecting in a substantially radial direction from a longitudinal axis of the shaft portion 120′. The shaft portion 120′ is arranged to be generally coaxial with a stationary gear 122 that is provided in a fixed orientation with respect to the housing 110. The stationary gear 122 is arranged to engage a rotor phasing gear 132 of a rotor 130, the rotor 130 being rotatably coupled to the eccentric portion of the eccentric shaft 120.
In use the rotor 130 describes a rotation-translation motion within a cavity 112 formed in the housing 110, the cavity 112 having a trochoidal shape.
In the example of FIG. 1 the rotor phasing gear 132 is an internal gear whilst the stationary gear 122 is an external gear, the eccentric shaft 120 being arranged to rotate three times for each rotation of the rotor 130.
FIG. 2 shows a cross-section of a portion of the rotor 130 showing corner seal elements 150 provided in cut-out portions 131 of the rotor 130. The cut-out portions 131 are provided in each of three corners of each side face 130A of the rotor. Coil spring elements are provided between the corner seal elements and an internal face of the cut-out portion 131, the spring elements being arranged to urge the corner seal elements against a respective end plate (or ‘sidewall’ or ‘end face’) 112 of the housing 110. The corner seal elements 150 are arranged to be slidable within the cut-out portions 131.
A tip seal 160 is provided along a side of the rotor at each of three corners 130B of the rotor 130. Each tip seal 160 is provided in a recess 161 formed in the rotor 130. A leaf spring element 162 is arranged to urge the tip seal 160 against the sidewall 112 of the housing 110.